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POHow to TryDeserializeWithLengthPrefix when Stream may not contain complete Object
 

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  1. POHow to TryDeserializeWithLengthPrefix when Stream may not contain complete Object
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    <p>I'm working on a new Buffering processor for our application and have had a fresh look at the Protobuf <code>Deserialize*</code> methods and have investigating using the following code, in my former version I had my own TypeIdentifier and LengthPrefix in front and then guaranteeing that I have a full block to Deserialise. For testing I have replaced my reading of a networkStream with reading random length chunks from a File written to disk using repeated calls into <code>SerializeWithLengthPrefix()</code></p> <p>But when I am traversing the mDatabuffer I get the <code>EndOfStreamException</code> being thrown. It's no big deal, just wanted to make sure I'm doing this correctly, as there is no guarantee that I will have a "full" block of data to process perfectly through the Deserialize call. I was initially doing TryReadLengthPrefix, but this seems cleaner.</p> <pre class="lang-vb prettyprint-override"><code>Public Sub New(ByVal maximumPacketSize As Integer) mMaxSize = maximumPacketSize mDataBuffer = New MemoryStream() mTypeResolver = AddressOf PacketTypeResolver End Sub Public Sub ProcessBuffer(ByVal theData() As Byte, offset As Integer, ByVal bytesToRead As Integer) 'append the data we have just received into our StreamBuffer so we can '"move back" if we hit the end of stream whilst Deserializing mDataBuffer.Seek(0, SeekOrigin.End) mDataBuffer.Write(theData, offset, bytesToRead) mDataBuffer.Seek(0, SeekOrigin.Begin) While mDataBuffer.Position &lt; mDataBuffer.Length Dim currentPosition As Integer = CType(mDataBuffer.Position, Integer) Try Dim p As Object = Nothing If Serializer.NonGeneric.TryDeserializeWithLengthPrefix(mDataBuffer, PrefixStyle.Base128, mTypeResolver, p) Then If GetType(BasePacket).IsAssignableFrom(p.GetType) Then Dim bufferedPacket As BasePacket = CType(p, BasePacket) ''''Do stuff with the packet. End If End If Catch ex As EndOfStreamException Dim tmpData As New MemoryStream() tmpData.Write(mDataBuffer.GetBuffer(), currentPosition, CType(mDataBuffer.Length - currentPosition, Integer)) mDataBuffer.Dispose() mDataBuffer = tmpData Exit While Catch ex As Exception Debug.Print(ex.GetType.Name &amp; "---" &amp; ex.Message) Throw End Try End While End Sub </code></pre> <p>(aside) For learning I'm wondering about the API design decision of not catching the exception inside <code>TryDeserializeWithLengthPrefix</code></p>
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